Refrigerating system including flow control valve

ABSTRACT

The compressor delivers hot compressed refrigerant to the condenser. Flow from the condenser to the evaporator is regulated by a thermostatic expansion valve having its sensing points (pressure and temperature) located in the compresser suction line downstream of an evaporator outlet control valve which is the new part in this application. This control valve has a piston type valve which is operated by a pilot valve actuated by the bellows in the suction line. The bellows is part of a charged system incorporating the capillary tube and the feeler bulb positioned in the evaporator fins. The charging fluid is selected to have a different thermal coefficient of expansion than the bulb so that the pilot valve will close at a selected temperature indicative of incipient icing conditions in the evaporator as may be found in air conditioning systems in which the compressor capacity can exceed the evaporator capacity (typical in automotive air conditioning). When the pilot valve closes pressure on the piston valve balances and the spring closes, the piston valve leaving a bleed port open to insure proper lubrication and cooling of the compressor.

[ l June 18, 1974 [57] ABSTRACT The compressor delivers hot compressed refrigerant to the condenser. Flow from the condenser to the evaporator is regulated by a thermostatic expansion valve having its sensing points (pressure and temperature) located in the compresser suction line downstream of an evaporator outlet control valve which is the new part in this application. This control valve has a piston type valve which is operated by a pilot valve actuated by the bellows in the suction line. The bellows is part of a charged system incorporating the capillary tube and the feeler bulb positioned in the evaporator fins. The charging fluid is selected to have a different thermal coefficient of expansion than the bulb so that the pilot valve will close at a selected. temperature indicative of incipient icing conditions in the evaporator as may be found in air conditioning systems in which the FLOW CONTROL VALVE Inventor: Charles D. Orth, Cedarburg, Wis.

Assignee: Controls Company of America,

Schiller Park, Ill.

Nov. 10, 1972 Appl. No.: 305,258

1 Int. F25b 41/04 Field of Search 62/217, 210, 224, 225

References Cited $2 a a. w l. l A illll 7/ llllllllllflllllflfffll .1 m V 4 Claims, 4 Drawing Figures compressor capacity can exceed the evaporator ca pacity (typical in automotive air conditioning). When the pilot valve closes pressure on the piston valve balances and the spring closes, the piston valve leaving a bleed port open to insure proper lubrication and cool- REFRIGERATING SYSTEM INCLUDING FLOW CONTROL VALVE BACKGROUND OF THE INVENTION In automotive air conditioning systems the compressor capacity may greatly exceed the evaporator capacity (load) and provision against icing the evaporator coil (which results in loss of evaporator effect) is made. U.S. Pat. No. 3,667,247 shows a system having a crosscharged thermostatic expansion valve located so its pressure and temperature sensing points are downstream of an evaporatoroutlet control valve. Evaporator outlet control valves may be responsive to pressure or temperature (they are related) in the evaporator. This invention is directed to a refrigerant control valve primarily designed to function as an evaporator outlet control valve but capable of use as a thennostatic expansion valve, a condenser by-pass valve or to control a media other than refrigerant. When used as a fin temperature evaporator outlet control valve this valve allows faster pull down of the system than permitted by other evaporator outlet control valves.

SUMMARY OF THE INVENTION This valve is provided with a sensing or feeler bulb located in the fins of the evaporator to directly sense the temperature and reduce flow from the evaporator when icing conditions prevail. While an evaporator pressure regulator valve would impair fast pull down by restricting flow this valve allows full flow until icing conditions prevail, thus allowing faster pull down of the system while providing full protection against icing the evaporator. While the primary sensing is at the fins there is a secondary effect at the bellows which will cause the selected control temperature to drift upward when the refrigerant temperature in the suction line (at the bellows) is very low. This is desirable in that it results in anticipator effect under those conditions whereas the control temperature is lower with moderate suction line temperatures. When this valve is used with the cross-charged thermostatic expansion valve of U.S. Pat. No. 3,667,247 the system performance is a marked improvement over the art. Whereas the usual evaporator outlet control valve will prevent extremely low pressures in the evaporator (since such low pressures are normally indicative of icing conditions) the present valve, responding to fin temperature, will sense the warm condition during pull down and remain open to allow maximum flow until the evaporator has actually cooled to icing conditions. This by itself facilitates rapid system pull down. The thermostatic expansion valve of the patent senses pressure and temperature downstream of the evaporator outlet control valve and under pull down conditions will open (rather than close as with the conventional thermostatic expansion valve) to maximize evaporator usage, thus further enhancing rapid pull down.

DESCRIPTION OF THE DRAWINGS FIG. I is a schematic view of the valve in a refrigeration system.

FIG. 2 is a vertical section through the present valve and a thermostatic expansion valve.

FIG. 3 is an enlarged view of the coil showing the relationship of the sensing bulb to the fins.

2 FIG. 4 is a cross-section through FIG. 3 on line 4-4.

DESCRIPTION OF THE PREFERRED EMBODIMENT The drawings illustrate the fin temperature responsive pilot operated control valve 10 combined with a thermostatic expansion valve 12 which is the preferred approach but the two could be separated. Refrigerant flows from compressor 14 to condenser 16, receiver 18 and then to inlet 20 of the thermostatic expansion valve. Cross bore 22 leads from the inlet 20 to chamber 24 which houses spring 26 compressed between valve support 28 and adjusting nut 30. The valve 32 controls flow past the seat and is actuated by push pin 34 which in turn is actuated by rider pin 36 fixed to diaphragm pad 38. Flow from the outlet 40 passes through the evaporator coil 42 to the inlet 44 of the control valve 10. In normal operation the control valve is open and to simplify this description the details of the control valve will not be considered at this point. Flow past the control valve passes over the rider pin 36 to outlet 46 and the compressor suction line 48. Pressure in the return conduit in the expansion valve can communicate with chamber 50 below the diaphragm 52 through port 54 in the upper wall 56 of the valve body. Leakage between rider pin and wall 56 is desired. Diaphragm 52 is mounted between the domed head 58 and support cup 60 threaded into the upper end of the valve body and sealed with respect thereto by means of O-ring 62. Head chamber 64 is cross charged with a temperature responsive charge through a capillary tube which is then sealed off.

The cross charge terminology connotes that the charging medium has a temperature/pressure curve other than the temperature/pressure curve of the refrigerant. In this instance it is selected to approach 0 superheat for the thermostatic expansion valve as the suction line pressure approaches 0 PSIG.

It will be noted that rider pin 36 is provided with a blind hole 66 which terminates at approximately the midpoint of the return flow path through the upper portion of the valve body. The blind hole, in effect, pro vides a small temperature sensing; chamber 68 inside the rider pin and located in the system return path downstream of the evaporator outlet control valve 10. Pin chamber 68 will always be colder than head chamber 64 and, therefore, the refrigerant charge will tend tocondense in chamber 68 and the control point will be at this location which is ideally situated. Since there is not much mass involved in the rider pin, the response of the valve would tend to be too rapid. To damp the hunting effect a low thermoconductivity sleeve 67 of Delrin (which is self-lubricating) is mounted over the rider pin.

To make the valve mountable in all positions capillary restricter 72 is fitted in the upper end of the rider pin. This then provides a very small capillary hole connecting the rider pin chamber 68 to head chamber 64. This is adequate for transfer of pressure changes but will minimize migration of any condensed refrigerant in chamber 68 to the head chamber should the valve be mounted unside down. Without this restricter there could be such migration with the result that the liquid refrigerant migrating to the head chamber (which is warmer) would flash to gas (increasing the pressure) and then promptly be recondensed in chamber 68. This would induce hunting in the system. With the restricter the hunting is minimized.

The details of this thermostatic expansion valve and its operation are fully explained in US. Pat. No. 3,667,247. 5

The control valve can under certain conditions override the normal functioning of the system. This valve includes a cylindrical member 70 fixed in the control body with support 72 captured between it and inlet 44. The support has a plurality of ports 74 allowing flow of refrigerant into the space between sleeve valve 70 and bellows 76 mounted on member 78 fixed in support 72. Capillary tube 80 connects to member 78 and, through the interior porting, to the interior of bellows 76. The bellows 76, tube 80 and feeler (sensing) bulb 82 are solid charged with a liquid having a thermal coefficient of expansion which is greater than that of the bulb. Since member 78 almost fills the space inside the bellows the effect of temperature on the bulb and the charge in the bulb becomes the dominant or controlling factor. Normally, therefore, the bulb temperature will control bellows movement. As bulb temperature falls liquid flows from the bellows to the bulb and the length of the bellows decreases. and vice versa. This is the controlling movement.

The right end of sleeve valve 70 supports cap 84 in which the pilot valve housing 86 is threadably mounted. The housing 86 is provided with a compressed spring 88 urging ball valve 90 to its seat 92. Pin 94 transmits movement from bellows 76 to pilot valve 90. A cylindrical main valve 96 fits within sleeve 70 and is axially movable between limits determined by stop 98 fixed inside sleeve 70 and stop 100 carried by cap 84. Spring 102 is compressed between cap 84 and the head 103 of valve 96 urges the valve to stop 98 where it closes off port 101 in sleeve 70 except for limited flow through port 102 in the side of the main valve. The head 103 of valve 96 is provided with a small bleed hole 104 allowing flow into the space 105 between the valve head 103 and cap 84. Flow to the bleed hole is filtered by screen 106. The push pin slides in the end of valve 96 and flow along the pin is limited by packing 108.

When pilot valve 90 is open fluid flows from the space 105 between valve head 103 and cap 84 faster than it flows into the space through the bleed hole 104. Therefore there is a pressure differential across the valve head. This pressure differential is great enough to overcome spring 99 and allow the main valve to move to the right (to stop 100) the expose ports 101 in sleeve 70 and allow normal flow through the entire system. When pilot valve 90 closes, the pressure builds up in space 105 and return spring 99 moves valve 96 to the left to shut off flow except for limited flow through port 102 to insure enough refrigerant to the compressor to avoid compressor damage.

The feeler bulb is mounted in the fins 110 at a location most likely to ice up first. This can be done simply by piercing the fins with a tool of proper size to accept the bulb. The bulb, therefore, senses fin temperature where icing will likely occur. Contrary to the usual evaporator outlet control valve which tends to retard pull down from a hot starting condition, this valve will insure maximum pull down simply because it responds to fin temperature and not to evaporator pressure or temperature. It will not reduce flow until actual icing conditions obtain. Thus, in an automotive air conditioning system (i.e., one having excess compressor capacity in many situations), on starting up on a hot day there is need for rapid pull down. With this control valve, full flow is permitted until the fin temperature is actually down to icing conditions. Other control valve would throttle flow prematurely. The present valve achieves faster pull down. During pull down the present thermostatic expansion valve insures full flow rather than throttling flow as characteristic of conventional thermostatic expansion valves. Therefore, the present control valve combined with this thermostatic expansion valve provides optimum performance during pull down. When icing conditions prevail flow is reduced to that passing port 102 to insure adequate flow to cool and lubricate the compressor. At this time the thermostatic expansion valve responds to low suction pressure and temperature and, by reason of its cross-charge will tend to maintain (open at) a lower superheat. This results in increasing flow to the evaporator but the temperature at the bellows will get lower than normal and the effect of reduced temperature at the bellows is to raise the response temperature of the control valve a few degrees. This is an anticipator effect and is desirable in that at very low refrigerant temperatures the setting drifts upward to anticipate icing conditions. In normal conditions this valve permits normal operation and the superheat setting of the thermostatic expansion valve moves up to normal which means the bulb controls the control valve at its normal set temperature.

By changing the main valve ports relative to the sleeve the main valve can be made to open and close oppositely to the pilot valve. Other control signal sources can be used if desired.

1 claim:

1. In a refrigeration system of the compressor, condenser, evaporator type having a thermostatic expansion valve regulating flow to the evaporator, the improvement comprising,

control valve means for regulating flow from the evaporator to prevent formation of ice on the evaporator when compressor capacity exceeds evaporator load,

means responsive to the temperature of the evaporator fins at a location likely to ice up first to close said valve means at a predetermined response temperature indicative of icing conditions,

said valve means passing a limited flow when closed to supply enough refrigerant to the compressor to cool and lubricate the compressor,

said temperature responsive means including sensing means located in the flow path between the evaporator and the compressor and responsive to abnormally low refrigerant temperature to cause said response temperature to drift upward and close said valve means in anticipation of icing conditions at said location.

2. Apparatus according to claim 1 in which said temperature responsive means includes a bulb located in the fins said sensing means comprising a bellows,

a capillary tube connecting the interior of the bellows to the interior of the bulb,

a liquid charge in the bulb, tube and bellows having a thermal coefficient of expansion different than that of the bulb whereby temperature changes at the bulb cause liquid to flow into or out of the bel-' lows and result in movement of the bellows,

whereby an abnormally low temperature at the bellows causes the overall response temperature of the bulb, tube and bellows to rise.

4. Apparatus according to claim 3 in which the thermostatic expansion valve is cross-charged and responsive to temperature and pressure: downstream of said valve means. 

1. In a refrigeration system of the compressor, condenser, evaporator type having a thermostatic expansion valve regulating flow to the evaporator, the improvement comprising, control valve means for regulating flow from the evaporator to prevent formation of ice on the evaporator when compressor capacity exceeds evaporator load, means responsive to the temperature of the evaporator fins at a location likely to ice up first to close said valve means at a predetermined response temperature indicative of icing conditions, said valve means passing a limited flow when closed to supply enough refrigerant to the compressor to cool and lubricate the compressor, said temperature responsive means including sensing means located in the flow path between the evaporator and the compressor and responsive to abnormally low refrigerant temperature to cause said response temperature to drift upward and close said valve means in anticipation of icing conditions at said location.
 2. Apparatus according to claim 1 in which said temperature responsive means includes a bulb located in the fins said sensing means comprising a bellows, a capillary tube connecting the interior of the bellows to the interior of the bulb, a liquid charge in the bulb, tube and bellows having a thermal coefficient of expansion different than that of the bulb whereby temperature changes at the bulb cause liquid to flow into or out of the bellows and result in movement of the bellows, means connecting the bellows to the valve means whereby bellows movement operates said valve means.
 3. Apparatus according to claim 2 in which the interior of the bellows contains a solid mass largely filling the interior to reduce the effects of temperature changes outside the bellows, said bellows being located in the refrigerant flow path between the evaporator and said valve means whereby an abnormally low temperature at the bellows causes the overall response temperature of the bulb, tube and bellows to rise.
 4. Apparatus according to claim 3 in which the thermostatic expansion valve is cross-charged and responsive to temperature and pressure downstream of said valve means. 